1. Field of the Invention
The present invention relates to a tray for Housing semiconductor devices such ICs, and more particularly to a tray suited for housing semiconductor devices having leads on every lateral side.
2. Description of the Prior Art
As the semiconductors such as ICs have been integrated more and more, they have become miniaturized more and more and thinner and thinner. Thus, it has become necessary to apply as small vertical loads and external shocks as possible to the devices, and the structure of the trays greatly influences the yield of the semiconductor devices.
Many semiconductor devices have extremely wi ring leads consisting of extremely thin metal wires extending externally from the semiconductor devices, and such a problem arises that leads are likely to be deformed or bent when the leads contact the corresponding inner walls of the pockets or the like in a tray.
Conventionally, trays for semiconductor devices whose cross sections are shown in FIGS. 8a and 8b are used in order to prevent the leads of the device from contacting the inner walls of the trays.
Each of trays 26, piled up as shown in FIG. 8a, is provided with pressing ribs 27 on its undersurface. The pressing ribs 27 of the upper tray 26 press semiconductor devices 29 in the pockets 28 of the lower tray 26 from above so that it is tried not to move but to fix the devices 29.
Each of trays 30, piled up as shown in FIG. 8b, is provided with pressing ribs 31 on its undersurface. A step portion 32 is formed in the inner edge portion of the lower end of each pressing rib 3. The step portions 32 of the pressing ribs 31 press the upper peripheral edges and the upper portions of lateral sides of semiconductor devices 34 so that it is tried not to move the devices 34 vertically or horizontally.
As described above, the trays as shown in FIGS. 8a and 8b fix the semiconductor devices 29 and 34 so that it is tried not to move but to fix the semiconductor devices horizontally. In this way, leads extending from the lateral sides of the semiconductor devices do not contact the inner walls of the pockets of the trays.
In the trays 26 and 30 as shown in FIG. 8a and 8b, the semiconductor devices 29 and 34 are pushed downward by the pressing ribs 27 and 31. When many trays are piled up, lower devices are applied with more vertical loads and are likely to be deformed more.
However, the lateral side portions of the lower part of each semiconductor device are not held in the trays 26 and 30 as shown in FIGS. 8a and 8b. Thus, such a problem arises that semiconductor devices are likely to be moved horizontally in the pockets and the leads of the devices are likely contact the inner walls of the pockets and are likely to be damaged, although trial is made to prevent horizontal movement of the devices in the pockets.